The electrical concept is very attractive, the mechanical implementation might
be an area of concern. Things that move (with precision) up in the wind and
weather, etc. are always an area of concern. However, sufficiently rugged
designs are clearly possible. One thing to watch out for would be the fact
that you have the highest current in the element right at the center, where all
the mechanical stuff and wiper contacts are. And, in general, the more gain
the antenna has, the higher the currents from mutual coupling. Kraus discusses
the loss impact of element currents in a closely spaced W8JK, and similar
discussions in the ham literature (one of the antenna compendiums has an
article by Brian Beezley that I'm thinking of).
Interestingly, another similar approach is putting computer controlled tuning
networks in each element (that is, loading coil/capacitors in the middle).
There's nothing that says you can't make the elements "electrically" shorter or
longer, instead of mechanically. You'd have to watch losses in your networks,
though.
What sort of reliability have people observed for other "actuator at the
antenna" designs: screwdrivers and compact loops spring to mind. Both of the
latter are often operated close to the ground, and maintenance, cleaning, etc.,
are much more convenient, (as opposed to at the top of a tower).
Dale L Martin wrote:
>
> Go to yahoo.com and type in 'steppir antenna' in the search field. You will
> get 7 hits.
>
> 73,
> dale, kg5u
> What about a web site URL to visit so we can learn
> > more?
> >
> >
>
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